With the recent tendencies of miniaturization and increased speed of electronic devices and combination of various functions thereof, signal transmission speed in electronic devices or signal transmission speed to the outside of electronic devices is increasing. Thus, a printed circuit board using an insulator with a lower dielectric constant and dielectric loss factor than those of the existing insulator is required.
Previously known bonding sheets and coverlays are generally made of an adhesive epoxy resin composition, but the dielectric constant increases due to the unique properties of the epoxy resin, and thus it is not easy to lower the dielectric constant and dielectric loss factor of the final product. Further, since elastomers commonly used in the adhesive epoxy resin composition such as butadiene/acrylonitrile (CTBN) with a carboxylic group end, etc. also have a high dielectric constant and dielectric loss factor, there was a certain limit to the application for more micronized and highly integrated semiconductor devices.
For example, Korean Registered Patent No. 0072808 discloses an adhesive tape including: a liquid epoxy resin; a solid resin; and a micro-capsule type of curing agent, and the adhesive tape can secure high heat resistance or adhesion to a substrate, but it is difficult to secure a low dielectric constant due to the use of a high content of epoxy resin having a high dielectric constant, and there is no suggestion of a method for lowering a dielectric constant or dielectric loss factor.
In addition, Japanese Laid-Open Patent Publication No. 2013-170214 discloses an epoxy resin composition including an epoxy resin, rubber components including maleic anhydride modified hydrogenated styrene butadiene rubber as a main component, polyphenylene ether, and an inorganic metal salt of a phosphorus compound, and the epoxy resin composition has high adhesion to a polyimide substrate and can secure high moisture tolerance, but there is no suggestion of a method for lowering a dielectric constant or dielectric loss factor.